const uniquePaths = (m, n) => {
  const dp = new Array(m).fill(0).map(i => new Array(n).fill(0))

  for (let i = 0; i < m; i++) {
    dp[i][0] = 1
  }

  for (let j = 0; j < n; j++) {
    dp[0][j] = 1
  }

  for (let i = 1; i < m; i++) {
    for (let j = 1; j < n; j++) {
      dp[i][j] = dp[i-1][j] + dp[i][j-1]
    }
  }

  return dp[m-1][n-1]
}

console.log(uniquePaths(3,2));